Question

Which equation best represents the law of conservation of mass?

mass of reactants > mass of products
mass of reactants - mass of product = mass conserved
mass of reactants = mass of products
mass of reactants + mass of products = mass conserved


What can the arrow in a chemical reaction be translated to mean? Check all that apply.

yields
accompanied by
react to form
added to
except



The expression CaCO3 → CaO + CO2 is an example of a

reactant.
product.
chemical equation.
chemical progression.






In the product 6O2, what does the coefficient mean?

There are 12 molecules of O2,
There are 8 molecules of O2,
There are 6 molecules of O2.
There are 2 molecules of O2.



Which additional product balances the reaction H2SO4 + 2NaOH → Na2SO4 + ________?

2H2O
2OH
H2O2
H3O


Cecil writes the equation for the reaction of hydrogen and oxygen below.

H2 + O2 → H2O

Why does his teacher ask him to balance the equation by including the correct coefficients?

to show that most molecules exist in pairs
to show that most compounds exist in pairs
to show that atoms are conserved in chemical reactions
to show that atoms are created in chemical reactions



Examine the chemical reaction.





What coefficient of O2 should be added so the number of atoms of oxygen is conserved on both sides of the reaction equation?

3
5
7
10



In a process called photosynthesis, plants use carbon dioxide and water, along with energy from sunlight, to produce sugar and oxygen. Photosynthesis is represented by the equation

What must a plant need to produce 4 molecules of sugar?

6 molecules of CO2
6 molecules of H2O
18 molecules of CO2
24 molecules of H2O



Franklin was performing an experiment by combining hydrochloric acid and sodium hydroxide. He measured the mass of his reactant materials to be 35g. The reaction resulted in the production of salt and water. He reported that his products weighed 32g.

Which best describes the results of Franklin’s experiment?

No error occurred, some of the products are always lost as heat.
An error occurred, the mass of the reactants should equal the mass of the products.
An error occurred, the products should weigh more than the reactants.
No error occurred, water is not weighed when determining the weight of the products.


Rust results from iron’s reaction to oxygen. An iron nail gains mass when it rusts. How does this reaction support the law of conservation of mass?

The mass of the rusted nail equals the mass of iron and the oxygen from the air it reacted with to form the rust.
The mass of the rusted nail increases because iron attracts more protons from the air.
The increased mass of the rusted nail is an exception to the law of conservation of mass since the rusted nail’s mass increases.
The increased mass of the rusted nail results from the rearrangement of protons and neutrons within oxygen, according to the law of conservation of mass.

Answer 1

1) mass of reactants = mass of products

2) Arrow in a chemical reaction (check all that apply):
- yields
- react to form

3) CaCO3 → CaO + CO2 is an example of a chemical equation.

4) In 6O2, the coefficient means: There are 6 molecules of O2.

5) The additional product is: 2H2O

6) Cecil’s teacher asks him to balance the equation: to show that atoms are conserved in chemical reactions

7) Coefficient of O2 to balance P4 + O2 → P4O10: 5

8) To produce 4 molecules of sugar the plant must need: 24 molecules of H2O

9) Franklin’s results: An error occurred, the mass of the reactants should equal the mass of the products.

10) Rust example: The mass of the rusted nail equals the mass of iron and the oxygen from the air it reacted with to form the rust.